The purpose of this cross-sectional study is to investigate characteristics of sleep in 45 symptomatic and 15 asymptomatic perimenopausal women (ages 45-55 years), 15 premenopausal women (45-55 years) and 15 postmenopausal women (50-60 years). Subjects who are psychologically normative, within 15% of ideal body weight, not taking estrogen, insomnia or depression drug therapy, non smokers, and with have no history of major physical or mental illness will sleep in a laboratory for two consecutive nights, one for adjustment and one for measurement. Selection criteria for perimenopause are reported menstrual cycle changes, including amenorrhea of not more than 2 years duration, elevated follicle stimulating hormone (FSH) level and/or reported insomnia, hot flash or depressive symptoms. These criteria are absent in premenopausal women and amenorrhea of at least eight years characterizes the postmenopausal group. The major aims are to 1) describe and compare sleep patterns including latency to sleep onset, sleep fragmentation, arousals an sleep structure; 2) describe 24 hour body temperature rhythms; 3) determine the incidence of hot flashes and periodic breathing (apneas and hypopneas) and their effect on sleep; 4) determine whether plasma ovarian steroid hormones are associated with sleep disturbances, periodic breathing or depression; and 5) determine the relationships between symptoms of depression, reported insomnia, hot flashes and disturbed sleep. Sleep will be monitored by EEG, EOG, and EMG using standardized procedures; periodic abnormal breathing with impedence pneumography, and nasal and buccal thermistors; body temperature with ambulatory monitoring of rectal temperature; hot flashes with a skin thermistor and resistance electrodes; hormones by serum radioimmunoassay; depression with two interview-observer rating scales; and menopausal symptoms with a self-report instrument. Data analysis will be directed to determining differences in sleep between symptomatic and asymptomatic perimenopausal women and women with premenopausal and postmenopausal status. In addition, tests of association between the variables will be done: including relating the frequency of hot flashes and periodic breathing with sleep patterns; hormone levels with sleep patterns, periodic breathing, and depression; and symptoms with disturbed sleep patterns.